Hundreds of thousands of people have rallied in central Beirut in a massive Hezbollah-led protest against the government of Prime Minister Fuad Siniora.

Lebanese troops and police cordoned off the prime minister's office compound in downtown Beirut and closed all roads leading to the area.

Protesters waved the Lebanese flag and called for the ouster of the pro-Western prime minister. Tents have also been erected for what protesters say will be an indefinite sit-in outside government offices.

Hezbollah chief Hassan Nasrallah on Thursday accused the current government of incompetence.

Hezbollah, a Shi'ite militant group, is demanding a new national unity government. Prime Minister Siniora has vowed to resist efforts to oust him, saying there is no way to remove a government except through parliament.

Shi'ite support for Hezbollah increased following the 34-day war earlier this year between the militant group and Israel.

Six ministers from the Hezbollah and Amal parties quit the government in November because their demands for more power were not met.

Tensions have been high in Beirut since the November 21 assassination of anti-Syrian politician Pierre Gemayel.